1. Field of the Invention:
This invention is related to a painting apparatus for a vehicle body wherein the vehicle body of a motorcar or the like is automatically painted.
2. Description of the Prior Art:
In prior art vehicle painting apparatuses, a vehicle body is arranged to be conveyed at a constant speed and passed longitudinally through a long painting booth including plural stages disposed in a line longitudinally. A bell-type atomizer, attached to a reciprocator, is provided at left and right positions or at a top position at desired selected stages to reciprocate upwards and downwards or leftwards and rightwards for electrostatically painting an outer panel region of the vehicle body. A painting robot carrying an air-spray gun attached thereto is provided at other selected stage(s) for electrostatically painting an inner panel region of the vehicle body. Thus, when the vehicle body has been passed through the paint booth, the body has the inner and outer panel regions already painted.
This conventional type of vehicle painting apparatus, however, is troublesome in maintenance and inspection thereof, because different kinds of painting devices are used. In particular, the reciprocator is equipped with a bell-type atomizer, and the painting robot is equipped with an air-spray gun. Accordingly, a modification thereof has been considered in which the painting robot equipped with the air-spray gun attached thereto which is used for painting both the outer panel region and the inner panel region of the vehicle body.
However, this modified type of painting apparatus is defective in that the electrostatic painting efficiency of the air-spray gun is low, i.e., about 40% in paint transfer efficiency. Thus, it becomes necessary to carry out a supplementary or additional painting, resulting in the lowering of productivity. In addition, the sprayed paint disperses in all directions in a wide range, and therefore, for preventing the dispersion of the sprayed paint to an adjacent stage, it is necessary that a partition means be provided between the mutually adjacent stages. The partition means can be opened and closed at will. If there is no partition means, than a large space is formed between the adjacent stages. The partition means can give rise to such problems as increased cost for installation thereof and increased spaces.
In addition, if the vehicle body is painted while being conveyed at a constant speed, there is a problem in that the vehicle body is liable to be out of position as a result of the vibrations of the conveyor. A defective or unreliable painting of the vehicle body can thus result.
In another type of prior art painting apparatus, a vehicle body is conveyed and then is stopped at the interior of a paint module which is arranged to be completely sealed. Under the sealed condition, the vehicle body is painted over the inner panel region and the outer panel region thereof, by plural painting robots disposed in the paint module. This type of apparatus, however, is defective in that the time for keeping the vehicle body in its stopped condition is very long, so that the apparatus cannot be synchronized with the tact-conveying motion of the production line, and thus is not suitable for large production.
There has been developed and put on the market a light weight and small-sized bell-type atomizer. This is an improvement of the heavy weight and large-sized bell-type atomizer known in the prior art.